RVT Ultrasound Physics and Instrumentation 3

Question 1

Acoustic shadowing distal to a calcified vessel wall is caused by:

Accepted Answer

High reflection and absorption at the calcified interface preventing sound transmission

Answer

Refraction of the beam away from the region of interest

Answer

Side lobes generated by the transducer array

Answer

Reverberation between two highly reflective surfaces

Question 2

A mirror image artifact in Doppler ultrasound refers to:

Accepted Answer

A duplicate spectral waveform appearing on the opposite side of the baseline

Answer

Double-imaging of a vessel on both sides of a strong specular reflector

Answer

Replication of color flow signals at twice the actual vessel depth

Answer

A symmetric color alias pattern in a stenotic jet

Question 3

Harmonic imaging improves image quality primarily by:

Accepted Answer

Using second-harmonic frequencies generated within tissue to reduce near-field clutter and side-lobe artifacts

Answer

Increasing the transmitted frequency to improve lateral resolution

Answer

Doubling the PRF to reduce aliasing at depth

Answer

Applying post-processing filters to sharpen vessel borders

Question 4

Lateral resolution in ultrasound imaging is best at the:

Accepted Answer

Focal zone of the transducer

Answer

Near field (Fresnel zone) directly below the transducer face

Answer

Far field (Fraunhofer zone) at maximum depth

Answer

Depth equal to half the wavelength

Question 5

The ALARA principle in diagnostic ultrasound stands for:

Accepted Answer

As Low As Reasonably Achievable

Answer

As Large As Reasonably Adjustable

Answer

Amplitude Levels Are Regulated Accordingly

Answer

Attenuation Limits Are Reached Appropriately

Question 6

Reverberation artifact in ultrasound appears as:

Accepted Answer

Multiple equally spaced echoes distal to a highly reflective interface

Answer

A bright focus with distal enhancement behind a fluid-filled cyst

Answer

A dark shadow distal to a calcified lesion

Answer

A duplicate image on the opposite side of a specular reflector

Question 7

Continuous-wave (CW) Doppler is preferred over pulsed-wave Doppler for measuring very high velocities because CW Doppler:

Accepted Answer

Has no Nyquist limit and therefore does not alias regardless of velocity

Answer

Uses a higher frequency carrier wave that shifts the Nyquist limit upward

Answer

Samples only a discrete gate along the beam to improve velocity accuracy

Answer

Automatically corrects for the Doppler angle using beam-steering algorithms